In order to calculate the brake slip, which is defined by EQU S=1-Vr/Vfr
known methods of brake slip control usually employ a reference speed Vref, which is formed either with reference to the wheels or with reference to the vehicle, instead of the free-rolling (unbraked) wheel peripheral speed Ffr. Because, generally speaking, EQU Vref.cent.Vfr
the "relative slip" calculated from Vref EQU Sref=1-Vr/Vref
does not correspond to the absolute slip either. WO 89/02382, for example, describes a method for obtaining Vref and for control to a desired relative slip.
In many applications (for example the control of vehicle yaw motion or transverse motion and observation units for yaw and transverse motion), it is necessary to know the absolute slip as accurately as possible.
The object of the invention is to make it possible to estimate the actual free-rolling wheel peripheral speeds and the vehicle longitudinal speed so that the absolute slip and other derived values can be more accurately determined.